The aim of this study is to further investigate the influence of the distribution and metabolism of ara-C in BDF1 mice bearing Sarcoma 180 in solid tumor or ascites form and to further search for other experimental models suitable for such experiments. Uptake, distribution, possible metabolism and excretion of 14C-tetra-hydrouridine (THU) and derivatives will be studied in humans. The influence of THU upon the half-life, metabolism and excretion of 3H-ara-C in humans will be investigated. The influence of THU on deoxycytidine kinase(s) extracted from murine and tumorous tissues will be evaluated.